I would like to know if I am stringing at 28lbs in manual machine, what should be the tension to be given in an electronic machine. Whether it should be same at 28lbs or higher?
Assuming it's a constant pull electronic machine you should lower the tension 10%, over a lock-out (crank) machine. If you want to maintain the same dynamic tension. If it were using a drop weight machine, then you can keep it at the same tension.
The "effective" tension resulting from a manual machine depends a great deal on the stringer himself, but in general it will be lower than that proivded by a constant pull (electronic or drop-weight). This "10%" figure has been around for a while, but I've yet to see a detailed study on the subject.
I have a Wise 2086. Recently I got it back from service. The Constant Pull Feature was not active after remounted it on my machine. When tested the unit, I was using Syn Gut set to 60lbs. After activating the tensioner, I saw it reach the reference tension of 60 lbs, then drop to 54lbs within a few seconds. Which surprised me, because the machine was recently serviced and re-calibrated. Then I realized that the Constant Pull Feature was turned off. I also verified with two digital scales that my unit was displaying the correct tension. The Wise 2086 Pro is one of the few machines that allows you to turn off Constant Pull, and then it becomes a Lock-Out machine. My Babolat Sensor is a straight CP only machine, there is no way to disable that feature, but why would you?
The vast majority of non-pro players are used to lockout tensions, simply because it's the most prevalent home stringer's machine. Rather than faff around knocking percentages off, disabling the CP is a lot easier. It's a very well thought out addition to the WISE, IYAM.
Here is a great video on the subject: [video=youtube;tzvaGE88RPI]http://www.youtube.com/watch?v=tzvaGE88RPI[/video]
Lock out tensions are inconsistent at best. Even if you turn the crank consistently, it does not always lock out at the exact reference tension. If your rational is true, then why even have an electronic tensioner at all? After switching from a lock-out to a Wise 2086 Pro, I've notice my stringbed to be more consistent than with any lock-out. What is more important is achieving the same dynamic tension as that of a previous stringing. If it means knocking off a few pounds off the reference tension, then so be it. The current rule of thumb is about 10%, believe it or not, that your prerogative. Stringing is about being consistent, not inconsistency.
